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SplitBit-Emulator/makefile
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AnachronautandClaude Opus 5 83623a3df3 Give the Voyager a screen 
A tile engine on ports 0x30 to 0x3F, bringing one bank of video memory registered the way
the disk's buffer is. The CPU writes cell indices and the device turns them into pixels,
which is the whole reason a screen is affordable at a megahertz: a frame is 16,667 cycles,
a full 320 by 200 picture is 64,000 bytes, and a 40 by 25 map is 2,000. A program that
changes two cells writes four bytes. The cost of a screen becomes the number of cells that
changed rather than the number of pixels on it.

Which makes colour depth free, so the tiles are eight bits: an 8 by 8 cell is 64 pixels and
each picks independently out of 256 colours, with no per-cell limit of the kind that made a
Spectrum two and C64 multicolour four. The low nibble of a cell's attribute is ADDED to
every index in its tile, sixteen at a time, so a tile drawn in 0 to 15 appears in any of
sixteen schemes without a second copy in tile memory - and a tile wanting all 256 leaves the
nibble at zero and gets them. Neither use costs the other anything.

Two decisions are arithmetic rather than taste, and both come from the machine having no
multiply. A map row is a page whether the mode fills it or not, so a cell address is the row
number as the high byte and the doubled column as the low byte with no arithmetic at all;
otherwise every cursor move on a 40 column screen would cost a row-times-40 in software. And
a palette entry is four bytes rather than three, so entry n is at n times four, a shift.

THE MAP IS A RING and the Scroll register says which of its 128 rows is on top. Scrolling
moves a register and no memory: blitting a 40 by 25 screen up one line is 1,920 bytes inside
one bank, which is twelve percent of a frame even with the controller widened, and a program
printing one page would spend six frames shuffling memory. It is now one port write - and
the rows that scrolled off are still there, which is where a terminal gets scrollback it
never had.

The device is part of the machine rather than part of the window. It renders into a buffer
that is a pure function of video memory, so the same program draws the same picture with
nobody watching; Voyager puts that buffer on the glass and decides nothing. Both binaries
take --screen, which saves a PPM when the machine stops, and that is what makes a screen
checkable on a host with no display at all.

Tests/video.sh checks fourteen named behaviours rather than comparing a recorded image,
because a recorded image would say "something changed" and leave which of the palette, the
tile, the attribute, the map or the scroll register broke to be found by hand. Verified by
breaking three things in turn: the additive nibble failed exactly one check, the scroll
origin exactly two, and moving every cell one pixel sideways exactly the four about
placement.

Tests/docs.sh could not count past nine, which is how a suite of ten scripts reported
itself as wrong for the wrong reason.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
2026-08-28 22:11:13 -04:00

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Makefile
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# SplitBit Emulator and Assembler Makefile
# Anachronaut
# 10/16/2024
# Compiler and flags
CC ?= gcc
CFLAGS ?= -Wall -Os
PREFIX ?= /usr/local
# Have the compiler write out which headers each object depends on, so that
# editing a header rebuilds everything that includes it.
DEPFLAGS = -MMD -MP
# The emulator and the assembler use POSIX interfaces that ISO C does not have:
# realpath, clock_gettime,
# strdup, dirname and getopt. Asking for POSIX.1-2008 by name means the build does
# not rely on the compiler happening to default to a mode where those are visible,
# and it survives someone overriding CFLAGS, which is why it is kept separate.
#
# _XOPEN_SOURCE=700 IS POSIX.1-2008, plus the XSI extensions. The plain
# _POSIX_C_SOURCE=200809L was here and is not quite enough: realpath is an XSI interface,
# so under -std=c11 -pedantic it went undeclared and the assembler would not compile. The
# ordinary build never noticed, because without -std=c11 the compiler's own default
# already declares it. The README makes a claim about the strict build, so 'make strict'
# below settles it rather than leaving it to be discovered.
POSIXFLAGS = -D_XOPEN_SOURCE=700
# Directories
SRC_DIR_EMU = Source/Emulator
SRC_DIR_ASM = Source/Assembler
SRC_DIR_DSK = Source/DiskTool
SRC_DIR_LINT = Source/Linter
OBJ_DIR = Object
# Source files
#
# MACHINE_SRCS is the machine itself, and both front ends link all of it. What separates
# SplitBit from Voyager is one file each: a terminal or a window. Anything that drifts out
# of the shared list and into one of those is behaviour the other does not have, which is
# the thing this split exists to prevent.
MACHINE_SRCS = machine.c io.c controller.c video.c utility.c cpu.c bootstrap.c assembly.c rom.c
EMU_SRCS = emulator.c $(MACHINE_SRCS)
VOY_SRCS = voyager.c $(MACHINE_SRCS)
ASM_SRCS = Assembler.c assembly.c firstPass.c Assm-util.c secondPass.c
DSK_SRCS = SplitDisk.c
LINT_SRCS = Linter.c
EMU_OBJS = $(EMU_SRCS:%.c=$(OBJ_DIR)/%.o)
VOY_OBJS = $(VOY_SRCS:%.c=$(OBJ_DIR)/%.o)
ASM_OBJS = $(ASM_SRCS:%.c=$(OBJ_DIR)/%.o)
DSK_OBJS = $(DSK_SRCS:%.c=$(OBJ_DIR)/%.o)
LINT_OBJS = $(LINT_SRCS:%.c=$(OBJ_DIR)/%.o) $(OBJ_DIR)/assembly.o
# Output binary names
EMU_TARGET = SplitBit
VOY_TARGET = Voyager
ASM_TARGET = Assembler
DSK_TARGET = SplitDisk
LINT_TARGET = SplitLint
# ---- Whether this machine can build Voyager ----
#
# PROBED BY BUILDING SOMETHING, not by looking for a file. A header that is present with no
# library behind it, or a library that needs flags this does not pass, would both pass a
# file check and then fail at link time, which is a much worse way to find out. If this
# compiles and links, so will Voyager.
#
# pkg-config first because that is what a packaged Raylib provides, and a bare -lraylib
# after it because a Raylib built from source usually does not install one.
RAYLIB_CFLAGS := $(shell pkg-config --cflags raylib 2>/dev/null)
RAYLIB_LIBS := $(shell pkg-config --libs raylib 2>/dev/null)
ifeq ($(strip $(RAYLIB_LIBS)),)
RAYLIB_LIBS := -lraylib -lm
endif
HAVE_RAYLIB := $(shell printf '#include <raylib.h>\nint main(void){return (int)GetTime();}\n' \
| $(CC) -x c - -o /dev/null $(RAYLIB_CFLAGS) $(RAYLIB_LIBS) 2>/dev/null \
&& echo yes)
# Default target: the machine, its three host-side tools, and Voyager where it can be built.
#
# VOYAGER IS NOT IN THE HARD LIST. Everything below it - the assembler, the disk tool, the
# linter, the whole test suite - has to build on a machine with no graphics library at all,
# because a project about a small understandable CPU should not need OpenGL to run its
# tests. Where Raylib is missing, 'make' says so once and builds everything else.
TOOLS = $(EMU_TARGET) $(ASM_TARGET) $(DSK_TARGET) $(LINT_TARGET)
ifeq ($(HAVE_RAYLIB),yes)
all: $(TOOLS) $(VOY_TARGET)
else
all: $(TOOLS)
@echo "Raylib was not found, so Voyager was not built. Everything else is here."
endif
# ---- The ROM the machine wakes up in ----
#
# Generated from the assembly rather than committed, because a copy of a program kept
# beside the program is a copy that goes stale. It needs the assembler, which is built
# first; that is a real dependency and saying so is better than hiding it.
#
# od and awk rather than xxd, which is not everywhere, and rather than python, which the
# README does not ask anybody to install to build this.
$(SRC_DIR_EMU)/rom.c: Programs/Boot/stage1.asm $(ASM_TARGET)
@mkdir -p $(OBJ_DIR)
@./$(ASM_TARGET) Programs/Boot/stage1.asm -o $(OBJ_DIR)/stage1.bin > /dev/null
@{ \
echo '// rom.c'; \
echo '// GENERATED from Programs/Boot/stage1.asm by the makefile. Do not edit.'; \
echo '//'; \
echo '// The first thing the machine runs, and the only part of it that is not on'; \
echo '// the disk. On hardware this is a chip; here it is an array, placed into'; \
echo '// Program Memory at reset the way a shadowed ROM is.'; \
echo ''; \
echo '#include "rom.h"'; \
echo ''; \
echo 'const unsigned char bootROM[] = {'; \
od -v -An -tu1 $(OBJ_DIR)/stage1.bin | awk '{ printf " "; for (i = 1; i <= NF; i++) printf " %s,", $$i; print "" }'; \
echo '};'; \
echo ''; \
echo 'const unsigned long bootROMBytes = sizeof(bootROM);'; \
} > $@
$(OBJ_DIR)/rom.o: $(SRC_DIR_EMU)/rom.c $(SRC_DIR_EMU)/rom.h
# Emulator binary
$(EMU_TARGET): $(EMU_OBJS)
$(CC) $(CFLAGS) -o $(EMU_TARGET) $(EMU_OBJS)
# Voyager: the same machine with a screen and a speaker. Its own object for the front end,
# and the shared ones for everything that is actually the machine.
$(VOY_TARGET): $(VOY_OBJS)
$(CC) $(CFLAGS) -o $(VOY_TARGET) $(VOY_OBJS) $(RAYLIB_LIBS)
$(OBJ_DIR)/voyager.o: $(SRC_DIR_EMU)/voyager.c
mkdir -p $(OBJ_DIR)
$(CC) $(CFLAGS) $(POSIXFLAGS) $(RAYLIB_CFLAGS) $(DEPFLAGS) -c $< -o $@
# Assembler binary
$(ASM_TARGET): $(ASM_OBJS)
$(CC) $(CFLAGS) -o $(ASM_TARGET) $(ASM_OBJS)
# Compile emulator source files to object files
$(OBJ_DIR)/%.o: $(SRC_DIR_EMU)/%.c
mkdir -p $(OBJ_DIR)
$(CC) $(CFLAGS) $(POSIXFLAGS) $(DEPFLAGS) -c $< -o $@
# Disk tool binary
$(DSK_TARGET): $(DSK_OBJS)
$(CC) $(CFLAGS) -o $(DSK_TARGET) $(DSK_OBJS)
# Assembly source linter. The instruction table is shared with the assembler and
# emulator so that adding an opcode cannot leave the linter with a private copy.
$(LINT_TARGET): $(LINT_OBJS)
$(CC) $(CFLAGS) -o $(LINT_TARGET) $(LINT_OBJS)
$(OBJ_DIR)/Linter.o: $(SRC_DIR_LINT)/Linter.c
@mkdir -p $(OBJ_DIR)
$(CC) $(CFLAGS) $(POSIXFLAGS) $(DEPFLAGS) -c $< -o $@
# Compile disk tool source files to object files
$(OBJ_DIR)/%.o: $(SRC_DIR_DSK)/%.c
@mkdir -p $(OBJ_DIR)
$(CC) $(CFLAGS) $(POSIXFLAGS) $(DEPFLAGS) -c $< -o $@
# Compile assembler source files to object files
$(OBJ_DIR)/%.o: $(SRC_DIR_ASM)/%.c
mkdir -p $(OBJ_DIR)
$(CC) $(CFLAGS) $(POSIXFLAGS) $(DEPFLAGS) -c $< -o $@
# Pull in the header dependencies written out by the compiler above.
-include $(EMU_OBJS:.o=.d) $(ASM_OBJS:.o=.d) $(DSK_OBJS:.o=.d) $(LINT_OBJS:.o=.d)
# ---- The strict build the README promises ----
#
# "The sources are ISO C and build clean under -std=c11 -pedantic with -Wall -Wextra."
# That is a claim somebody may check by typing it, so the suite checks it first. It was
# false when this target was written: realpath went undeclared under a feature test macro
# that did not reach far enough, which the ordinary -Os build never saw.
STRICT = -std=c11 -pedantic -Wall -Wextra -Werror $(POSIXFLAGS)
#
# VOYAGER IS CHECKED SEPARATELY, and only where Raylib is. It includes raylib.h, so putting
# it in the loop below would make 'make test' fail on exactly the machines the two-binary
# split exists to support - and it would not be noticed here, where Raylib is installed.
strict:
@for source in $(SRC_DIR_EMU)/*.c $(SRC_DIR_ASM)/*.c $(SRC_DIR_DSK)/*.c $(SRC_DIR_LINT)/*.c; do \
case "$$source" in *voyager.c) continue ;; esac; \
$(CC) $(STRICT) -c $$source -o /dev/null || exit 1; \
done
ifeq ($(HAVE_RAYLIB),yes)
@$(CC) $(STRICT) $(RAYLIB_CFLAGS) -c $(SRC_DIR_EMU)/voyager.c -o /dev/null
endif
@echo "The sources build clean under -std=c11 -pedantic."
# Run the test suite against the programs in Programs/
test: all strict
@./Tests/lint.sh
@echo
@echo
@./Tests/run.sh
@echo
@./Tests/voyager.sh
@echo
@./Tests/disk.sh
@echo
@./Tests/cycles.sh
@echo
@./Tests/video.sh
@echo
@./Tests/terminal.sh
@echo
@./Tests/native.sh
@echo
@./Tests/agree.sh
@echo
@./Tests/docs.sh
# Rebuild all three tools with the address and undefined behaviour sanitizers and run
# the test suite under them. Slower than 'make test', and worth running before a
# release or after anything that touches memory handling.
#
# THE WHOLE SUITE, which it did not used to be: it built all three tools sanitized and
# then ran only run.sh and terminal.sh, so SplitDisk was compiled with the sanitizers and
# never exercised, and native.sh - which drives the assembler and the emulator harder than
# anything else here - was skipped. Those are the parts where block arithmetic on disk
# images and buffer indexing in two assemblers live, which is exactly what the sanitizers
# are for. Adding the three of them costs about six seconds.
#
# The sanitizers catch reads and writes off the end of an array, use after free,
# leaks, and undefined arithmetic. What they do NOT usefully catch here is uninitialised
# memory: AddressSanitizer's junk fill is a toolchain default this build does not
# configure, there are six heap allocations in the repository and the largest is a
# deliberate calloc, and the machine's own memories are static arrays it never touches.
#
# If the suite fails, the sanitizer binaries are deliberately left in place so
# that the failing case can be run again by hand. 'make' puts the normal ones back.
SANITIZE_FLAGS = -Wall -Wextra -g -O1 -fsanitize=address,undefined -fno-omit-frame-pointer
sanitize:
@$(MAKE) --no-print-directory clean
@$(MAKE) --no-print-directory CFLAGS="$(SANITIZE_FLAGS)"
@echo "Running the test suite under AddressSanitizer and UndefinedBehaviorSanitizer."
@./Tests/lint.sh
@echo
@./Tests/run.sh
@echo
@./Tests/voyager.sh
@echo
@./Tests/disk.sh
@echo
@./Tests/cycles.sh
@echo
@./Tests/video.sh
@echo
@./Tests/terminal.sh
@echo
@./Tests/native.sh
@echo
@./Tests/agree.sh
@echo
@./Tests/docs.sh
@$(MAKE) --no-print-directory clean
@$(MAKE) --no-print-directory
@echo "Sanitizer run finished cleanly. Normal binaries rebuilt."
# Record the current output of every test as the expected result.
# Only do this when the current output is known to be correct.
bless: $(EMU_TARGET) $(ASM_TARGET)
@./Tests/run.sh --bless
# Clean up object and binary files
clean:
rm -rf $(OBJ_DIR)
rm -rf Tests/build
rm -f $(SRC_DIR_EMU)/rom.c
rm -f $(EMU_TARGET) $(ASM_TARGET) $(DSK_TARGET) $(LINT_TARGET) $(VOY_TARGET)
# Install compiled binaries
install: $(EMU_TARGET) $(ASM_TARGET) $(DSK_TARGET) $(LINT_TARGET)
mkdir -p "$(PREFIX)/bin"
install -m 755 $^ "$(PREFIX)/bin/"
# Phony targets
.PHONY: all clean install test bless sanitize
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